As natural gas is an odorless gas, it is vital to odorize it in residential regions to avoid explosion or inhalation poisoning. Hence, odorizing units are installed in city gate stations due to safety manners. Odorant systems may be alternative depending on system requirements, but all of them shall guarantee a constant odorization ratio at every gas flow rate. Injecting the odorant to the natural gas medium by means of a metering pump is the most accurate way of odorization that usually used for higher gas capacities. An injection odorizer mainly includes an odorant storage tank, a pump and instruments to control and transfer the odorant to gas line. Bypass odorizing systems are preferably used for pressure reducing stations with low flow rate (up to 10,000 SCMH), where inexpensive method is required. In this method, the odorant will be conducted to the gas from a bypass flow from an odorant storage tank by means of an appropriate differential pressure caused usually by a butterfly valve or an orifice in the main line. Shiraz Mechanic as a manufacturer of odorizing units and metering pumps, has the capability to produce the desired odorizer in every circumstances.